const matchHtmlRegExp = /["'&<>]/;

/**
 * Escape special characters in the given string of text.
 *
 * @param  {string} string The string to escape for inserting into HTML
 * @return {string}
 * @public
 */

export function escapeHtml(string: string = ''): string {
  const str = '' + string;
  const match = matchHtmlRegExp.exec(str);

  if (!match) {
    return str;
  }

  let escape;
  let html = '';
  let index = 0;
  let lastIndex = 0;

  for (index = match.index; index < str.length; index++) {
    switch (str.charCodeAt(index)) {
      case 34: // "
        escape = '&quot;';
        break;
      case 38: // &
        escape = '&amp;';
        break;
      case 39: // '
        escape = '&#39;';
        break;
      case 60: // <
        escape = '&lt;';
        break;
      case 62: // >
        escape = '&gt;';
        break;
      default:
        continue;
    }

    if (lastIndex !== index) {
      html += str.substring(lastIndex, index);
    }

    lastIndex = index + 1;
    html += escape;
  }

  return lastIndex !== index
    ? html + str.substring(lastIndex, index)
    : html;
}